System for visualisation of optical marking on an opthalmic lens, stmap-marking device and method for orientation of lenses using such a system

ABSTRACT

The system comprises a light source, supplying an incident light beam illuminating the ophthalmic lens. On the optical path of the incident beam, reflecting means are arranged downstream from the ophthalmic lens and a collimation and magnifying lens is arranged upstream from the ophthalmic lens. A camera, the lens, the ophthalmic lens and the reflecting means are arranged on the same main optical axis. The reflecting means comprise a plurality of flat reflecting faces, arranged in the form of at least one cube corner block open in the direction of the ophthalmic lens. The flat faces can form a matrix of adjacent cube corner blocks made of plastic.

BACKGROUND OF THE INVENTION

The invention relates to a system for visualisation of optical markingsof an ophthalmic lens, comprising

-   -   a light source supplying an incident light beam illuminating the        ophthalmic lens,    -   on the optical path of the incident beam, reflecting means        arranged downstream from the ophthalmic lens and a collimation        and magnifying lens arranged upstream from the ophthalmic lens,    -   a camera, the lens, the ophthalmic lens and the reflecting means        being arranged on the same main optical axis.

STATE OF THE ART

Conventionally, a laboratory machining progressive ophthalmic lensesuses semi-finished ophthalmic lenses, i.e. ophthalmic lenses theprogressive convex face whereof is finished and polished, to machine theconcave face of the ophthalmic lenses in order to obtain the finalcorrective powers. Before machining, the initial marking of themanufacturer, stamped on the convex face, is used to index theophthalmic lens. After machining, the ophthalmic lens is washed and canbe subjected to several treatments such as hardening, anti-glare, etc. .. . The initial marking then has to be erased. After treatment, theophthalmic lens has to be marked again.

As a general rule, the operator looks for the micro-etchings 1,represented in FIG. 1, characteristic of an ophthalmic lens 2, and makesa dot with a felt-tip pen on the two micro-etchings 1. These twomicro-etchings are generally two circles presenting a constant distancebetween axes of 34 mm. An addition 3 representative of certainproperties of the ophthalmic lens is also inscribed next to one of thetwo circles. Certain manufacturers add other lens identificationmicro-etchings, for example a number, a barcode, a dot-code, etc. . . .The operator then positions the ophthalmic lens 2 manually on astamp-marking machine and launches the stamp-marking process. Duringstamp-marking, represented in FIGS. 2 and 3, a pattern 4 c is depositedon the ophthalmic lens 2. Two patterns 4 a and 4 b, corresponding to aright ophthalmic lens, and two patterns 4 c and 4 d, corresponding to aleft ophthalmic lens, are etched respectively with specific grooves inleft and right engraving block supports 5, generally made of steel orceramic. The pattern 4 c to be deposited is transposed by means of anink container and a stamp which recovers the ink stored in the groove ofthe engraving block (4 c) and deposits it on the ophthalmic lenses 2.The circles in broken lines 6 correspond to the position of the inkcontainer at rest.

An optician who receives ophthalmic lenses uses the stamp-marking toindex the ophthalmic lens and close-cut it according to the shape of theframe. Once the ophthalmic lens has been close-cut and fitted, thestamp-marking is removed with alcohol.

Marking an ophthalmic lens with a felt-tip pin has the drawback of notbeing very precise and, for example, of leading to parallax errors.

OBJECT OF THE INVENTION

It is an object of the invention to remedy these drawbacks and, inparticular, to enable the optical markings of an ophthalmic lens to belocated precisely and quickly.

According to the invention, this object is achieved by the fact that thereflecting means comprise a plurality of flat reflecting faces, arrangedin the form of at least one cube corner block open in the direction ofthe ophthalmic lens.

According to a development of the invention, six flat reflecting faces,formed by mirrors, are arranged in the form of two cube corner blocks,arranged on each side of the main optical axis.

According to another development of the invention, the flat reflectingfaces, in the form of cube corner blocks, form a matrix of adjacent cubecorner blocks.

According to another feature of the invention, the system comprises atinted lens arranged on the main optical axis, between the lens and theophthalmic lens.

According to a preferred embodiment, the system comprises rotation meansfor making the reflecting means rotate around the main optical axis.

It is also an object of the invention to provide a device forstamp-marking ophthalmic lenses comprising at least one inking unit, astamp-marking unit and at least one visualisation system according tothe invention.

It is a further object of the invention to provide a method fororienting ophthalmic lenses, comprising placing of an ophthalmic lens ona support and adapting the position of the ophthalmic lens by means ofoptical markings visualised by at least one visualisation systemaccording to the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

Other advantages and features will become more clearly apparent from thefollowing description of particular embodiments of the invention givenas non-restrictive examples only and represented in the accompanyingdrawings, in which:

FIGS. 1 and 2 represent an ophthalmic lens respectively before and afterstamp-marking.

FIG. 3 shows etched left and right engraving blocks each comprising twodifferent patterns.

FIG. 4 represents a stamp-marking device comprising a visualisationsystem according to the invention.

FIGS. 5 and 6 represent cube corner blocks respectively in bottom viewand in top view.

FIG. 7 represents the functioning of a cube corner block.

FIG. 8 illustrates, in top view, a particular embodiment of thereflecting means of a system according to the invention.

FIG. 9 shows a monitor image corresponding to a left camera and a rightcamera of a device according to the invention.

FIG. 10 shows a particular embodiment of a light source.

FIG. 11 shows a particular embodiment of an ophthalmic lens support.

FIGS. 12 to 14 illustrate the stamp-marking method according to theinvention.

DESCRIPTION OF PARTICULAR EMBODIMENTS

In FIG. 4, a stamp-marking device comprises an inking unit 7, astamp-marking unit 8 and a visualisation system 9 of optical markings,for example micro-etchings 1, of an ophthalmic lens 2. A light source10, for example formed by a light-emitting diode, is arranged next to amain optical axis S and supplies an incident light beam 11 thatilluminates the ophthalmic lens 2 by means of semi-reflecting means 12arranged on the main optical axis S between a camera 13 and acollimation and magnifying lens 14. The semi-reflecting means 12 reflectthe incident light beam 11 in the direction of the ophthalmic lens 2 andtransmit a detection beam 11′ originating from the ophthalmic lens 2 inthe direction of the camera 13. It is advantageous for the camera 13 tobe of the high-resolution 795 (H)×596 (V) Charge Coupled Device (CCD)type. An Automatic Gain Control (AGC) camera is preferably chosen inorder to preserve a single integration time (exposure time of thephotosensitive cells).

The semi-reflecting means 12 can be formed, for example, by asemi-reflecting mirror, oriented at 45° with respect to the main opticalaxis S, or by a semi-reflecting cube. However the semi-reflecting mirroris more advantageous for reducing optical aberrations and is less bulky.The collimation and magnifying lens 14 can for example be a flat-convexlens or an achromatic lens enabling spherical aberration to beminimised.

On the optical path of the incident beam 11, reflecting means 15 arearranged downline from the ophthalmic lens 2 whereas the collimation andmagnifying lens 13 is arranged upline from the ophthalmic lens 2. Thecamera 13, lens 14, ophthalmic lens 2 and reflecting means 15 arearranged on the same main optical axis S. The reflecting means 15comprise a plurality of flat reflecting faces 16 arranged in the form ofcube corner blocks open in the direction of the ophthalmic lens 2. Theflat reflecting faces 16 can be formed by mirrors. In FIG. 4, two cubecorner blocks, arranged on each side of the main optical axis S, areformed by six flat reflecting faces 16 formed by mirrors.

The reflecting means 15 are fixed, for example stuck, onto a securingdisk 17 fixedly secured to a motor 18 forming rotation means enablingthe reflecting means 15 to be rotated around the main optical axis S.Balancing of the reflecting means 15 and disk 17 with respect to themotor 18 is indispensable for vibration-free rotation. The motor 18,having a rotation frequency typically comprised between 700 and 3000rpm, enables the lighting of the image to be homogenized during theintegration time of the camera 13. It also contributes to suppressingthe edges of the cube corner blocks from the image.

The ophthalmic lens 2 is held by a fixing suction pad 19 which isconnected to a carriage 21. A transparent protective plate 20 isarranged between the ophthalmic lens 2 and the reflecting means 15 forthe purposes of protecting the reflecting means 15. The protective plate20 is preferably toughened and anti-glare treated on both faces. Thesuction pad 19 typically has a diameter of 20mm and enables theophthalmic lens 2 to be held by negative pressure during stamp-marking.The material of the suction pad 19 does not leave any trace on theconcave face of the lenses. The assembly formed by the motor 18 andreflecting means 15 on the one hand, and the ophthalmic lens 2, suctionpad 19 and protective plate 20 on the other hand, can be driven by thecarriage 21, enabling the ophthalmic lens 2 to be moved between amarking position facing a marking axis A and a visualisation positionfacing the main optical axis S.

The visualisation system 9 preferably comprises a tinted lens 22arranged on the main optical axis S between the lens 14 and theophthalmic lens 2. The tinted lens 22 can be a lens of sun-glass type ora polarizing lens. It enables the lighting to be reduced in order not tosaturate the camera 13 and therefore to keep an optimum integration timewhatever the ophthalmic lens 2 used. The tinted lens 22 also contributesto suppressing the edges of the cube corner blocks from the image.

The lens of the camera 13 must be situated at the focal point on theimage side of the lens 14 to avoid vignetting and to thus preserve agood photometric efficiency. The lens of the camera 13 comprises means23 for adjusting the focussing and means 24 for adjusting the opening ofthe iris. Adjustment of the iris and of the focussing can be performedremotely by means of two servomotors, one servomotor 25 for focussingand one servomotor 26 for adjustment of the opening of the iris. Aminimum opening of the iris is preferable to have a better definition.The light-emitting diode constituting the light source 10 can have awavelength of about 650 nm and illuminate with a reduced diffusionangle. However it does require a diaphragm to adjust the light beamprecisely. In addition, the diode can be adjustable in intensity. It ispreferable to have a powerful lighting in order to use a minimum irisopening.

The stamp-marking device, represented in FIG. 4, also comprises amonitor 27, for example a liquid crystal display, connected to thecamera 13, and a safety gate 28 able to be raised and lowered by anactuator 29. t is preferable to use a camera 13 supplied in 5 VDC and amonitor 27 supplied in 12 VDC to eliminate stray signals.

In FIG. 5, a bottom view of a cube corner block enables the three edges30 of the three faces 16 of the cube corner block to be distinguished,whereas in FIG. 6, in top view, each of the three reflections 31 of eachedge 30 in the respectively opposite face 16 can also be seen.

As represented in FIG. 7, an incident light beam 11 is reflected by aflat reflecting face 16 a in the direction of a second flat face 16 breflecting light to the third flat face 16 c, the latter reflects lightin a direction parallel to the incident beam 11, but on an optical pathoffset with respect to the incident beam 11. The spatial offset 32depends on the position and direction of the incident beam 11 and can beat the maximum about the dimension of the cube corner block. The cubecorner block inverts an image composed of several incident beams 11.

In FIG. 8, a matrix 33 of adjacent cube corner blocks is arranged on asupport 34. The flat reflecting faces 16 are constituted by solid cubecorner blocks made of plastic, for example moulded plastic. The flatreflecting faces can also be formed by hollow cube corner blocks made ofplastic or by cube corner blocks machined in a metal support. A matrix33 of adjacent cube corner blocks enables the visualisation system 9 tobe made insensitive to the optical power of the ophthalmic lens 2 used.

FIG. 9 represents the image that can be displayed on the monitor 27. Thestamp-marking device can comprise two visualisation systems 9,respectively for a right ophthalmic lens 2 and a left ophthalmic lens.Thus, the images from two cameras 13 can be displayed alternately on themonitor 27, or simultaneously in the case where the device comprises twomonitors. Each image represents an ophthalmic lens 2, micro-etchings 1and the support means of the ophthalmic lenses 2, for example thesuction pads 19. On the monitor screen, indexing marks 36 are marked,enabling each ophthalmic lens to be oriented by means of themicro-etchings 1 and marks 36.

To orient the ophthalmic lens 2, the operator places the lens on thefixing suction pad 19 and rotates the lens slightly until he sees on thescreen the micro-etchings 1 having a distance of 34 mm between axes. Hepositions the two micro-etchings 1 perfectly in the indexing marks andcreates a vacuum to fix the ophthalmic lens onto the fixing suction pad19.

However, the grooves of the patterns 4 are never etched at the rightdistance with respect to a reference point of the engraving blocksupports 5. A software can then be used which enables the indexing marks36 to be inserted on the screen and which stores its own indexing marksfor each engraving block. The positions of the left and right marks 36,represented in FIG. 9, present a vertical offset 37, which is taken intoaccount on by means of the software used for image processing. Tocalibrate the stamp-marking device, the operator records a reference ofthe set of patterns 4 etched on the engraving block supports 5. He runsthe stamp-marking procedure and visualises the marked ophthalmic lens onthe screen of the monitor 27. Then, for example simply by means of acomputer mouse, he superposes the indexing marks. 36 on the stamp-markedcircles, with a distance of 34 mm between axes, to locate themicro-etchings 1. Different sets of engraving blocks can thus be usedusing the calibration and references of the sets of engraving blockswithout calibrating after each change of set of engraving blocks.

Operation of the visualisation system 9 thus consists in achieving animage of the surface of the ophthalmic lens 2 comprising themicro-etchings 1 on a matrix CCD camera. However, the micro-etchings 1are not non-homogeneities modulated in transmission, like for exampleprinted images, but phase non-homogeneities. Their contrast is thereforelow if they are observed without using their diffraction properties. Forthis, the ophthalmic lens 2 is preferably illuminated with a collimatedlight. To do this, a light source 10 filtered by a diaphragm situated atthe focal point of the lens 14 can be used. Moreover, to be as free aspossible from dependency on non-collimated ambient light, a narrowspectrum light-emitting diode can be used and a filter centred on itswavelength be placed after the lens 14. The beam thus formed passesthrough the ophthalmic lens a first time, undergoes reflection by thereflecting means 15, and passes through the ophthalmic lens a secondtime. It is then focussed at the focal point of the lens 14 where theentry of the lens of the camera 13 is placed.

This enables a maximum of flux to be collected and the lighting on thesurface of the camera 13 to be homogenized limiting vignetting. From theimagery point of view, the ophthalmic lens 2 bearing the micro-etchings1 must be situated at the focal point on the object side of the lens 14.The lens 14 then reflects back the image to infinity, an image that ispicked up by the lens of the camera 13 to be formed in the plane of thedetector. Focussing adjustment of the lens enables mechanicalpositioning tolerances to be relaxed. The cube corner blocks constitutethe reflecting means 15 enabling the micro-etchings 1 to be visualisedon non-zero power lenses. The cube corner blocks in fact reflect backthe received beams in a direction parallel to their angle of arrival.Passing through the ophthalmic lens 2 again with the same angle, theyare output from it again collimated.

FIG. 10 represents an alternative embodiment of the light source 10,enabling the semi-reflecting means 12 to be eliminated. The light sourceis an annular lighting with light-emitting diodes 38, arranged aroundthe main optical axis S, on a support 39 in the form of a ring. Thesupport 39 can be fixed upstream from the collimation and magnifyinglens 14, for example at the level of the lens of the camera 13. Thelight-emitting diodes 38 can also be replaced by optical fibres.

FIG. 11 represents an alternative embodiment of the support of theophthalmic lens. This support is formed by an annular seal 40, forexample a seal of V ring type or a toroidal sealing ring, arrangedbetween the ophthalmic lens 2 and the protective plate 20 which alsobecomes (for this alternative embodiment) the suction pad support. Theannular seal 40 typically has a diameter of 50 mm and presents theadvantage of being a more stable support means than the suction pad 19.

FIGS. 12 and 13 show the steps of a stamp-marking method, performedafter a first ophthalmic lens 2 has been positioned by means of thevisualisation system 9. In FIG. 12, the engraving block support 5advances on a linear guiding system 41, so as to position a firstpattern 4 b under the stamp-marking unit 8, arranged on the marking axisA. As represented by an arrow in FIG. 12, the stamp-marking unit isactuated so that the marking head 42 comes into contact with the firstpattern 4 b to transfer this pattern to the marking head 42. Theengraving block support 5 is withdrawn and the carriage 21 bearing thefirst ophthalmic lens 2 moves up to the marking axis A. As representedin FIG. 13, the stamp-marking unit is then actuated so that the markinghead 42 comes into contact with the first ophthalmic lens 2 to apposethe first pattern 4 b on the first ophthalmic lens 2.

Preferably, the stamp-marking device comprises two visualisation systemsand two stamp-marking units, the inking unit comprising two engravingblock supports 5 like, for example, the engraving block supports 5represented in FIG. 3. This enables simultaneous marking of twoophthalmic lenses, typically a right ophthalmic lens (R) and a leftophthalmic lens (L). The method of stamp-marking a second ophthalmiclens can in fact be performed in the same way as the steps of theprevious method. The patterns 4 b and 4 d are thus simultaneouslytransferred by the two stamp-marking units respectively onto the rightand left ophthalmic lenses.

As represented in FIG. 3, the engraving block supports 5 can comprisetwo different patterns 4 a and 4 b, intended for different rightophthalmic lenses, and two different patterns 4 c and 4 d, intended fordifferent left ophthalmic lenses. Thus, the stamp-marking devicerepresented in FIGS. 12 and 13 enables marking of another pair of rightand left ophthalmic lenses, requiring a third pattern 4 a and a fourthpattern 4 c, to be performed using the same pair of engraving blocksupports 5. In fact, as illustrated in FIG. 14, the engraving blocksupports 5 are moved so as to position the third pattern 4 a oppositethe marking head 42. Likewise, the fourth pattern 4 c is moved oppositethe corresponding marking head.

A device comprising the inking unit 7, the stamp-marking unit 8 and twovisualisation systems 9 according to the invention presents reduceddimensions and can be placed on a working surface. The stamp-markingunit has two marking heads, respectively for a right ophthalmic lens andfor a left ophthalmic lens. The operator positions the ophthalmic lenses2 manually on the lens support using two visualisation systems 9,respectively for a right ophthalmic lens and for a left ophthalmic lens.The device is however preferably equipped with a single screen 27,switching from one camera to the other being performed by means of aselector. Such a device enables parallax errors to be prevented andenables the ophthalmic lenses 2 to be stamp-marked with a greatprecision.

The invention is not limited to the particular embodiments described andrepresented above. In particular, the visualisation system 9 can be usedwithout performing stamp-marking, but only to identify or orient to thenmake a check, an additional micro-etching or another operation. Thevisualisation system 9 is particularly well suited in the case ofprogressive ophthalmic lens but can also be used for any type ofophthalmic lens.

1-14. (canceled)
 15. System for visualisation of optical markings of anophthalmic lens, comprising a light source, supplying an incident lightbeam illuminating the ophthalmic lens, on the optical path of theincident beam, reflecting means arranged downstream from the ophthalmiclens and a collimation and magnifying lens arranged upstream from theophthalmic lens, a camera, the lens, the ophthalmic lens and thereflecting means being arranged on the same main optical axis, systemwherein the reflecting means comprise a plurality of flat reflectingfaces, arranged in the form of at least one cube corner block open inthe direction of the ophthalmic lens.
 16. System according to claim 15,wherein the flat reflecting faces are constituted by solid cube cornerblocks made of plastic.
 17. System according to claim 15, wherein theflat reflecting faces are constituted by hollow cube corner blocks madeof plastic.
 18. System according to claim 15, wherein the flatreflecting faces are formed by mirrors.
 19. System according to claim18, comprising six flat reflecting faces formed by mirrors, arranged inthe form of two cube corner blocks, arranged on each side of the mainoptical axis.
 20. System according to claim 15, wherein the flatreflecting faces, in the form of cube corner blocks form a matrix ofadjacent cube corner blocks.
 21. System according to claim 15,comprising a tinted lens arranged on the main optical axis, between thelens and the ophthalmic lens.
 22. System according to claim 15, whereinthe light source is formed by a light-emitting diode arranged next tothe main optical axis, the incident light beam illuminating theophthalmic lens by means of the semi-reflecting means arranged on themain optical axis, between the lens and the camera.
 23. System accordingto claim 15, wherein the light source comprises several light-emittingdiodes, arranged in a ring around the main optical axis, upstream fromthe lens.
 24. System according to claim 15, comprising a transparentprotective plate between the ophthalmic lens and the reflecting meansand a fixing suction pad arranged between the ophthalmic lens and theprotective plate.
 25. System according to claim 15, comprising atransparent protective plate between the ophthalmic lens and thereflecting means and an annular seal arranged between the ophthalmiclens and the protective plate.
 26. System according to claim 15,comprising rotation means to make the reflecting means rotate around themain optical axis.
 27. Device for stamp-marking ophthalmic lensescomprising at least one inking unit, a stamp-marking unit andvisualisation means, device wherein the visualisation means are formedby at least one visualisation system according to claim
 15. 28. Methodfor orienting ophthalmic lenses, comprising placing an ophthalmic lenson a support and adjusting the position of the ophthalmic lens by meansof optical markings visualised by the visualisation means, wherein thevisualisation means are formed by at least one visualisation systemaccording to claim 15.